The technical field of this invention is phototherapy and, in particular, instruments employing optical fibers or other flexible waveguides to deliver radiation to a targeted biological site.
Fiber optic phototherapy is an increasingly popular modality for the diagnosis and/or treatment of a wide variety of diseases. For example, in surgery, infrared laser radiation will often be delivered to a surgical site via a hand-held instrument incorporating an optically transmissive fiber in order to coagulate blood or cauterize tissue. Other uses for optical fiber-delivered radiation include treatment of artheroscerotic disease and prostatic disease. U.S. Pat. No. 4,878,492 issued to Sinofsky et al., incorporated herein by reference, discloses the use of infrared radiation to heat blood vessel walls during balloon angioplasty in order to fuse the endothelial lining of the blood vessel and seal the surface. Another application of fiber-delivered radiation is disclosed in U.S. Pat. No. 5,053,033 (Clarke), incorporated herein by reference. Clarke teaches that retenosis following angioplasty can be inhibited by application of U.V. radiation to the angioplasty site to kill smooth muscle cells which would other wise proliferate in response to angioplasty-induced injuries to blood vessel walls.
Optical fiber-delivered radiation has further been used to treat prostate enlargement caused by Benign Prostate Hyperplasia (BPH) or prostate cancer. Such treatments include delivering the optical fiber transurethrally or hypodermically to apply therapeutic temperatures to the enlarged prostatic tissue.
Moreover, fiber optic delivery systems have been incorporated in endoscopic or catheter-based instruments to deliver radiation to a targeted biological site from within a body lumen or cavity. Typically, the fiber optic phototherapy device is inserted through an instrument lumen or catheter for delivery in-vivo.
Conventional optical fiber phototherapy devices can include an optical element, such as a focusing lens, that is coupled to the optical fiber by a cylindrical housing. The housing is typically a metallic band or cuff, constructed from stainless steel or gold, that is sized to hold both the lens and the optical fiber in a friction-tight fit. Alternatively, the housing can be glued to the optical fiber or can be threaded to facilitate connection to the fiber.
The performance of such conventional phototherapy devices incorporating a metallic housing has proven less than optimal for a number of reasons. In particular, when the phototherapy device is placed within the lumen of the delivery instrument for insertion into the patient, the metallic housing can scrape against the inner walls of the delivery instrument lumen and cause damage to the lumen.
Additional problems associated with such conventional phototherapy devices include loosening of the optical element due to thermal cycling, as the metallic housing and the optical element, as well as the optical fiber, have significantly different thermal characteristics, such as the coefficient of thermal expansion. Thus, during the application of radiation, the housing tends to expand greater than both the optical fiber and the optical element, resulting in loosening of the connection between the housing, the optical fiber and optical element. Thermal cycling can also result from sterilization procedures and during shipping of the phototherapy device.
Moreover, the effects of thermal cycling are magnified by the presence of the metallic housing which can absorb significant amounts of radiation from the optical fiber thereby further increasing the temperature of the housing. For example, a stainless steel housing can absorb approximately 40% of the incident radiation.
As the above described optical fiber phototherapy devices have proven less than optimal, it is an object of the present invention to provide improved phototherapy devices having a construction that permits insertion into the lumen of a delivery instrument without causing damage or significant wear to the lumen.
Another object of the present invention is to provide a phototherapy device including components parts constructed of materials chosen to reduce wear on the lumen of the delivery instrument.
Still another object of the present invention is to provide phototherapy devices including component parts having a similar thermal characteristics to inhibit the effects of heat cycling.
A further object of the present invention is to provide phototherapy devices that are simple and inexpensive to manufacture.
Another object of the present invention is to provide an improved method of making a phototherapy device.
Other general and more specific objects of this invention will in part be obvious and will in part be evident from the drawings and the description which follow.